evidence of amino acids and other organic material in space (but often both D & L forms)

questionable bacterial fossils in Martian rock

-However, this would imply that some other origin of life was likely because it would have had to happen elsewhere before it could be transported here, and the only difference would be that life did not originate on Earth.

Spontaneous origin on earth: primitive self-replicating macromolecules acted upon by natural selection ((macro)Evolution is one example of this)

-This is often attacked for the seeming impossibility for life to have been produced by a chemical reaction triggered by lightning and the ability of any produced DNA to actually be in a sequence that could produce a working model of life if replicated. It is also attacked for religious reasons, as it bypasses things like the idea of a supreme being directly creating humans. It also seems unlikely to some that such huge changes are possible in evolution without evidence of an "in-between stage" that is credible. Many of the stages of man are disputed due to their somewhat shakey grounds. For example, bones from other animals have been taken accidentally in some cases to be part of a humanoid, and complete skeletons have been sketched out from a limited number of bones.

Special creation: religious explanations (Intelligent Design is one popular example of this.) These explanations contend that life was created by God (or perhaps some other Intelligent Designer).

Proponents of Intelligent design suggest that the vast complexity of life could only have been intentionally designed while other creationists cite biblical support.

-This is often attacked for many of the same reasons that religion is attacked, and is often regarded as superstitious and/or unscientific.

It is debated as to whether schools should teach one hypothesis or the other when talking about the origin of life. However, since they are all currently known major hypotheses (and sometimes hypotheses proven wrong are shown for educational purposes), this wikibook includes what it can without discriminating unfairly against one hypothesis or the other.

Cells are very small and decompose quickly after death. As such, fossils of the earliest cells do not exist. Scientists have had to form a variety of theories on how cells (and hence life) was created on Earth.